Pressure relief valves are used in a variety of commercial, industrial and domestic applications to maintain a pressure within a container below a predetermined maximum pressure. Specifically, if the pressure within the container exceeds a start-to-discharge pressure or predetermined maximum pressure, the pressure relief valve will open to vent fluid to the atmosphere until the pressure within the container decreases below the predetermined maximum pressure. The amount and rate at which the fluid or vapor is vented to the atmosphere is associated with the magnitude of the pressure within the container.
Different pressure relief valves have different sizes, start-to-discharge pressures and flow capacities. A pressure relief valve may be selected for use with a container based on a design specification of the container such as a maximum pressure to which the container can be safely exposed without rupturing.
Known pressure relief valves often include a spring that exerts a force on a shaft to urge a valve plug towards a valve seat or seating surface. The spring is seated within a spring guide that maintains the spring in the proper position within the valve body. An adjusting nut may be threaded onto the stem, within the valve body, the adjusting nut being used to vary the amount of force exerted by the spring on the stem. A locking nut is threaded onto the stem behind the adjusting nut to prevent the adjusting nut from being loosened during use. Known pressure relief valves are generally expensive and time consuming to assemble due to the large number of internal parts.